Purely elastic interfacial instabilities in superposed flow of polymeric fluids

Effect of non-normal interactions on the interfacial instability of multilayer viscoelastic channel flows

“…As in the case of bulk flow instabilities mentioned above, significant progress has been made in understanding the onset conditions and the instability mechanisms of unidirectional interfacial and free surface viscoelastic flows [15][16][17][18][19][20]. Specifically, the mechanism of purely elastic interfacial instabilities has been demonstrated to be the coupling of the jump in the base flow normal stresses across the interface and the perturbation velocity field [15,16].…”

“…Specifically, it has been shown that in the two-layer flows the analysis can quantitatively describe the experimental findings in terms of the neutral stability diagram as well as the growth and decay rates of interfacial disturbances in the linear and weakly nonlinear regime provided that the analysis employs constitutive equations that can accurately predict both the steady and transient rheological properties of the experimental fluids [15][16][17][18][19][20][21][22][23][24][25]. On the other hand, similar studies in three-layer symmetric and asymmetric flows have yielded a less favorable comparison between the theoretical and experimental findings [16].…”

Short wave instability of co-extruded elastic liquids with matched viscosities

“…Related work on this phenomenon has been performed by Su and Khomami, who have studied analytically and numerically the stability of two-layer die flow [8,9], and Renardy, who tackled the short-wave behaviour of two-layer Couette flow [7]. More recently, Laure et al [5] have studied two-and three-layer Poiseuille flow of Oldroyd-B fluids, with long to moderate wavelength perturbations, incorporating the effects of surface tension, viscosity stratification, density stratification and inertia.…”

Elastic effects in superposed fluids

“…They found that the interface between the fluids is unstable if more than half of the channel's height is filled by the fluid with lesser elasticity among the two. In another paper 8 they show that the instability is a result of a discontinuity in the first normal stress difference at the interface of superposed fluids. Recently, Suman and Kumar 9 showed that elasticity of liquids manifests as an "effective inertia."…”